Hand held sanding and abraiding machine



May 12, 1959 G. M. NEFF HAND HELD SANDING AND ABRADING MACHINE Filed June 19, 1957 5 SheetS -Sheet 1 a/ z: m

l? Z /5 47 a: as I u 45 imp MNF/f E N I m M m I w "u m D G W S E H D M H May 12, 1959 Filed June 19; 1957 3 Sheets-Sheet y 2, 1959 G. M. NEFF HAND HELD SANDING AND ABRADING MACHINE 3 Sheets-Sheet 3 Filed June 19, 1957 United States Pate HAND HELD SANDING AND ABRAIDING MACHINE Gene M. Nefi, Racine, Wis., assignor to John Oster Manufacturing (30., Milwaukee, Wis., a corporation of Wisconsin Application June 19, 1957, Serial No. 666,589

3 Claims. (Cl. 51-170) This invention relates to hand held power driven surface finishing machines and refers more particularly to a sanding device of the type wherein a work performing unit or abrasive carrying plate having a substantially flat under surface is power driven for translatory agitation parallel to its under surface. in using a power driven sanding and abrading machine for finishing the surfaces of wood and similar grained materials, an orbital motion of the abrasive surfaced work performing unit is most efficient for rough sanding because the abrasive cuts faster and removes feather edges of the grain. However, such orbital motion of the abrasive leaves a relatively rough surface on the Work being finished, and for final finishing it is therefore much more desirable to employ a reciprocating motion, so that the machine may be oriented to have the work performing unit which carries the abrasive agitated along a path substantially parallel 'to the grain of the wood to thus produce a smoother finish.

Here'tofore portable machines of the type in question afforded either reciprocating motion or some form of orbital motion, but they could not be adjusted to provide either type of motion at the users option, except in a few instances where a conversion from one type of motion to another could be effected only after partial disassembly of the machine.

By contrast, it is an object of this invention to provide a hand held surface finishing machine of the character described having a work performing unit or pad adapted to carry an abrading or polishing "medium on its flat under side, and having power means for driving the work performing Lmit in translatory motion parallel to its under side, in which machine a simple, easily made adjustment provides for either reciprocatory or orbital motion of the work performing unit.

More particularly it is an object of this invention to provide a machine of the character described "having a power drive which may be alternatively caused to effect either reciprocatory or orbital motion of the abrasive carrying .plate, the selection of the desired type of motion being 'eflected by a very simple and expeditious adjustment requiring neither disassembly of any portion of "the machine nor removal of the polishing or abrading medium from the abrasive carrying plate.

Another object of this invention resides in the provision "of "a surface "finishing machine of the character described having a body which carries a power driven eccentric mounted for rotation on a vertical axis and having a work performing plate movably mounted beneath the body,'wherein a motion transmitting connection between'the eccentric andthe plate imparts reciprocatory motion to the'plate, and wherein a shiftable locking member is "movableto and from an operative position inwhichitestablishes a second motion trans- =mitting connection between the "eccentric and the plate 'wherbythe plate is constrained to orbital motion with "the eccentric.

Still another object of this invention resides in the provision of a surface finishing machine having the features described in the preceding statement of object, and wherein the locking member is simple and inexpensive and securely maintains said second motion transmitting connection operative despite the vibration which normally attends use of the machine.

A further object of this invention resides in the provision of a surface finishing machine of the character described having a body providing a power drive and having a work performing plate movably carried beneath the body by means of resilient legs projecting downwardly from the body, wherein the resilient legs mount the work performing plate for translatory motion parallel to its flat under surface, and wherein the resilient legs also cooperate with motion transmission means in confining said plate to back and forth reciprocation when the machine is adjusted for that type of motion.

It is another general object of this invention to provide a hand held abrading machine which is especially suitable for home workshop use by reason of its simplicity, ruggedness, versatility and low cost, but which at the same time possesses features that make it unusually well suited for professional use.

With the above and other objects in view which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claims, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claims.

The accompanying drawings illustrate several complete examples of the physical embodiments of the invention constructed according to the best modes so far devised for the practical application of the principles thereof, and in which:

Figure 1 is a view, partly in side elevation and partly in vertical section, of a surface finishing machine embodying the principles of this invention;

Figure 2 is a sectional view taken substantially on the plane of the line 22 in Figure 1;

Figure 3 is a disassembled perspective view of the machine shownrin Figure 1;

Figure 4 is a perspective view of one of the resilient members by which the work performing unit or abrasive carrying plate is mounted on the body of the machine;

Figure 5 is a cross sectional View taken on the plane of the line 5-5 in Figure 4;

Figure 6 is a perspective view of a modified embodiment of the resilient mounting member for the abrasive carrying plate of the machine of this invention; and

Figure 7 is a perspective View of another modified form of the resilient mounting for the abrasive carrying plate.

Referring now more particularly to the accompanying drawings, in which like numerals designate like parts throughout the several views, the portable surface finish ing machine of this invention is shown as an abrading machine or hand held sander. The machine comprises, in general, a hollow body 5 open at its bottom, an upright motor housing 6 mounted on the front of the body and containing an electric motor 7 and a handle 8 joined to and projecting rearwardly from the motor housing and accommodating a service cord and an electric switch 9 by which the supply of electric current to the motor may be controlled. Obviously other power drive means than an electric motor may be provided, as for example a compressed air motor.

Movably supported by the body in a position substantially closing its open bottom, is a work performing unit or abrasive carrying plate 12 having a substantially fiat under surface across which a sheet of abrasive or polish ing medium (not shown, but which may be ordinary sandpaper, for example) may be tensioned. The abrasive carrying plate, which is preferably rectangular and elongated in its front-to-rear dimension, is secured to the lower ends of a plurality of resiliently yieldable legs 14 fixed to and projecting downwardly from the body, so as to be supported by the body for translatory motion parallel to its flat under surface.

The driving torque of the motor shaft 10, which projects downwardly into the hollow interior of the body 5, is transmitted to the abrasive carrying plate through an eccentric 15 carried by the body for rotation on a vertical axis. As described in detail hereinafter, the eccentric at all times has a motion transmitting connection with the plate, by which connection the eccentric imparts back and forth reciprocation to the plate, and an adjustably movable locking member 16 on the plate provides for the establishment or disruption of a second motion transmitting connection between the eccentric and the plate whereby the plate may be constrained to orbital movement with the eccentric.

The eccentric is carried by a driven pulley 18 freely rotatably journaled, by means of a ball bearing 21, on a stub shaft 20, vertically fixed in the top wall of the body. An enlarged head on the lower end of the stub shaft supports the inner race of bearing 21 against downward displacement, and the bearing is seated in an upwardly opening concentric well 22 in the driven pulley. A split expansion washer 23 rests on the outer race of the bearing and engages in an annular groove in the circumferential wall of the well in the pulley to support the pulley.

The driven pulley is connected by means of a toothed traction belt 24 with a drive pulley 25 on the lower end of the motor shaft 10.

The eccentric itself comprises a ball bearing 27 mounted on a downwardly projecting pilot boss 26 on the driven pulley, parallel but eccentric to the axis of the stub shaft 20. The boss 26 fits in the inner race of the ball bearing 27, and downward displacement of the bearing is prevented by a split washer 28 engaged in an annular groove in the boss and engaged under the inner race of the bearing. The driven pulley is preferably provided with an eccentric counterweight 29 which counteracts the eccentric forces thereon and thus decreases the vibration to which the machine as a whole is subjected when in use.

A motion transmitting connection between the outer race of the eccentric bearing 27 and the abrasive carrying plate is provided by an elongated motion transmitting member 33 in the form of a lever. The lever 33 lengthwise overlies the upper surface of the abrasive carrying plate, and its front end has a pivotal connection with the plate, provided by an upright stud 34 fixed in the plate near its front end, midway between its side edges. The lower end portion of the stud 34 has a reduced neck which projects through a closely fitting hole in the plate and is peened over, as at 35, against the under side of the plate, to secure the stud in place. A bushing 36 in the motion transmitting member provides a good pivotal connection between it and the stud, and a split washer 37, engaged in an annular groove near the top of the stud, overlies the bushing to confine the motion transmitting member or lever to side to side swinging motion across the top of the plate. A second washer 37' loosely encircling the stud 34, may be interposed between the split washer and the bushing 36, if desired.

The motion transmitting member or lever is further constrained to horizontal swinging motion by means of a transversely extending guide rail 38, fixed on the plate and overlying the rear end portion of the motion transmitting member or lever. In front of this guide rail there is a collar 39 on the motion transmitting lever, projecting upwardly therefrom, in which the outer race of the lower ball bearing 27 is received to thus provide a driving connection between the eccentric and the motion transmitting lever.

As long as the motion transmitting lever is free to swing from side to side about the stud 34, only the back and forth or longitudinal components of the orbital motion of the eccentric will be imparted to the plate 12 by the lever, with the lateral components of eccentric rotation being taken up by side to side swinging of the motion transmitting member, relative to the plate. Hence, he resultant motion of the plate is back and forth reciprocation. But if the motion transmitting member is confined against swinging motion, the plate will be constrained to orbital motion with the eccentric, and for this purpose there is provided a second motion transmitting connection between the eccentric and the plate, com- PIlSlIlg the hereinbefore mentioned locking member 16 which is mounted on the upper surface of the plate, near the rear thereof and behind the rear extremity of the lever 33.

This locking means comprises a transversely extending supporting block 41 fixed on the upper surface of the abrasive carrying plate and having a threaded bore extending therethrough lengthwise of the plate, an adjusting screw 42 threaded in said bore, and a stop block 43 closely overlying the plate 12 and connected to the forward end of the adjusting screw to be translated back and forth thereby, toward and from engagement in a rearwardly opening notch 44 in the outer end of the motromtrapsmitting lever 33. The rear end portion of the ad ust ng screw, which at all times projects behind the supporung block 41 to be accessibly located near the rear of the abrasive carrying plate, may comprise a square section head 45 adapted to be actuated by a suitable key or socket wrench (not shown), and the front of the screw has a freely rotatable connection with the stop block, as at 46, by which the stop block is constrained to move back and forth in consequence of adjusting rotation of the screw.

When the stop block is in its rearmost position, out of engagement with the motion transmitting lever, as shown the latter is of course free for side to side swinging motion and the machine is set for back and forth reciprocation of the plate. However, when the screw is rotated in the direction to advance the stop block into locking engagement with the outer end of the motion transmitting lever, the second motion transmitting connection becomes operative and the plate is constrained to orbital motion with the eccentric.

To provide additional surface on the motion transmitting member against which the stop block may lockingly engage, a mating notched block 47 may be secured to the rear end portion of the motion transmitting member. The front of the stop block is wedgingly tapered, as at 48, and the notch in the block 47 has a corresponding forwardly convergent configuration so that as the stop block advances into engagement with the motion transmitting member the motion transmitting member will be cammingly swung toward alignment of its longitudinal center line with that of the plate, assuring a secure connection between the motion transmitting member and the stop block.

When the machine is set for back and forth reciprocation of the abrasive carrying plate, the friction and inertia forces in the mechanism will inevitably have some tendency to swing the plate from side to side, even though the second motion transmitting connection is disengaged. Such tendency to sidewise motion of the plate as is inherent in the structure, however, is inhibited by reason of the fact that the resilient legs 14 by which the plate is translatably mounted beneath the body are transversely stiifened to the extent necessary to resist such incidental sidewise motion, although they are still yieldable enough to permit the positively produced orbital motion f th plate when the second motion transmitting connection 15 s gg F r that u p the legs 14 of each pair iii thereof at the front and back of the plate may comprise integral parts of a single resilient inverted U-sha'ped mounting member 49. The two legs 14 of each mounting member are connected by a transverse bight or ridge 50 of the same resiliently flexible material that the legs are made of (rubber, neoprene or the like). The height of said ridge may be slightly over half that of the legs proper, and its width may average about one-third the diameter of the legs, although the dimensions of this stiffening strip are not critical, so long as it enables the legs to resist incidental lateral motion when the machine is adjusted for back and forth reciprocation, without interfering with lateral flexing of the legs when the machine is set for oscillation.

Bushings 51 at the bottoms of the legs are molded into the resilient material of the mounting member, and these bushings have downwardly opening threaded holes 52 by which the plate may be securely fastened to the legs, as by means of screws 53 extending upwardly through aligned holes in the abrasive carrying plate 12.

A rigid mounting strap 54 fixed to and extending across the top of each resilient mounting member, has downturned ends provided with threaded holes to receive screws 55 by which the strap, and consequently the mounting member is secured to the side wall on the body of the machine.

In the embodiment shown in Figure 6, the legs 14' of the resilient mounting member are individually molded of resilient material and are laterally stiffened by reason of the fact that each has a substantially elliptical crosssection with the major axis of the ellipse disposed crosswise of the plate.

In the embodiment shown in Figure 7, the legs 14 have a circular cross-section, as in the Figure 4 version, but instead of an integral stiffening ridge between them they are stiffened by a bow spring 56 medially secured to the mounting strap 54, as by means of a rivet 57, and having its end portions engaging the opposing lower portions of the two resilient legs.

Preferably a pad 59 of felt or the like is cemented or otherwise flatwise secured to the underside of the abrasive carrying plate 12 to cover the peened over lower end of the stud 34 and the heads of any rivets or the like which may protrude below the bottom surface of the plate 12, and to provide a cushioned backing for sandpaper or similar abrasive material tensioned thereover.

A clip 61 on the plate, near each end thereof, cooperates with the upper surface of the plate to clampingly grip an end portion of a sheet of abrasive and hold it in place. Each clip may be formed as a unitary stamping comprising a pair of opposite spring arms 62, a jaw member 64 having a substantially L-shaped cross section connected with an end of each spring arm, and a handle portion 65 connecting the two jaw members. Each of the spring arms is secured, at its end opposite the jaw member, to the abrasive carrying plate, near a side edge thereof, and is bent along its length to bias the jaw member at its other end downwardly into clamping engagement with the top of the plate. One leg of the L-shaped jaw member projects downwardly and has a substantially channel shaped pad 66 of rubber or the like secured thereto to provide a good gripping surface. The two clips are preferably identical, with their jaw members transversely aligned and endwise spaced apart, so that in the case of the rear clip the adjusting screw 42 may be accessible between the jaw members. The handle portion 65 of each clip spans the space between its jaw members and connects them for up and down clamping movement in unison, and it has an outwardly projecting flange 67 which facilitates raising the jaw members out of clamping engagement with the plate, to permit sandpaper, emery cloth or the like to be inserted under or withdrawn from beneath the jaws.

From the foregoing description, taken together with the accompanying drawings, it will be apparent that this invention provides a hand held surface finishing machine having an abrasive carrying plate which may be power driven in either orbital or back and forth reciprocating motion, and wherein the desired type of motion may be obtained with a simple and expeditious adjustment requiring no dissassembly of the machine or substitution of parts thereon.

What is claimed as my invention is:

1. In a portable sanding and abrading machine capable of either straight line or orbital sanding and abrading, the combination of: a body; a power driven eccentric beneath the body and supported therefrom for rotation on an upright axis; a vibratory plate at the underside of the body having means to secure a sheet of sand paper thereto to provide a downwardly facing abrading surface; resiliently yieldable leg means fixed to the body fore and aft of and substantially equispaced from the axis of rotation of the eccentric and secured to the adjacent portions of the plate to support the plate for edgewise motion with respect to the body; a lever lengthwise overlying the top of the plate between it and the underside of the body with the radial portion of the lever intersected by the axis of rotation of the eccentric; means pivotally securing one end of the lever to the plate near the forward leg means for side-to-side swinging movement of the lever across the top of the plate, the free end of the lever being near the aft leg means; a free running bearing connecting the medial portion of the lever with the eccentric so that said medial portion of the lever has circular orbital motion imparted to it by the eccentric, which motion of the lever imparts edgewise motion to the plate; resilient means stilfening the fore and aft leg means to substantially the same degree against lateral or side-to-side deflection so that the plate is more easily shifted forward and backward than from side-to-side, whereby the laterally stiffened leg means elfectively attenuates any tendency for the plate to move with the lever as it swings from side-to-side, and so that as long as the lever is free to swing relative to the plate the edgewise motion imparted to the plate by the eccentric acting through the lever is a straight line fore and aft reciprocation for straight line sanding and abrading; and means for rigidly interlocking the plate and lever to secure the lever against pivotal movement relative to the plate and thereby convert the machine to do orbital sanding and abrading, said means comprising a nut member fixed to the top of the plate between the free end of the lever and the adjacent edge of the plate with the axis of its threaded bore intersecting the axis of rotation of the eccentric, a screw threaded in said nut member, and solid abutments on the free end of the lever and on the inner end of said screw to be brought into and out of interengaging relationship by rotation of the screw.

2. In a portable abrading machine, the combination of claim 1 further characterized by the provision of means carried by the plate and engaging the free end portion of the lever to positively constrain all motion of the lever with respect to the plate to side-to-side swinging movement in a plane parallel with the plate.

3. In a portable sanding and abrading machine capable of either straight line or orbital sanding and abrading, the combination of: a body; a power driven eccentric beneath the body and supported therefrom for rotation on an upright axis; a vibratory plate at the underside of the body having means to secure a sheet of sand paper thereto to provide a downwardly facing abrading surface; a lever extending along the top of the plate, between it and the underside of the body, with the medial portion of the lever intersected by the axis of rotation of the eccentric; means pivotally securing one end of the lever to the plate and thereby providing for side-to-side swinging movement of the free end portion of the lever across the top of the plate; a free running bearing connecting the medial portion of the lever with the eccentric so that said medial portion of the lever has circular orbital motion imparted to it by the eccentric, which motion of the lever imparts edgewise motion to the plate; spaced apart resiliently yieldable leg means fixed to the underside of the body at diametrically opposite sides of the eccentric and secured to the adjacent portions of the plate to support the plate for edgewise motion with respect to the body, said leg means being spaced substantially equal distances from the axis of rotation of the eccentric and being stiffer to substantially the same degree against deflection in directions corresponding to the direction of side-toside motion of the free end portion of the lever than in directions substantially normal to said side-to-side motion so that said leg means effectively attenuates any tendency for the plate to move with the lever in the direction of side-to-side motion of its free end portion, while permitting edgewise straight line reciprocation of the plate in a direction normal to said side-to-side swinging motion of the free end portion of the lever, so that as long as the lever is free to swing relative to the plate the edgewise motion imparted to the plate by the accentric acting through the lever is said straight line reciprocation for straight line sanding and abrading; and means to rigidly interlock the plate and lever and thereby secure the lever against pivotal movement relative to the plate so as to convert the machine to do orbital sanding and abrading, said means comprising a nut member fixed to the top of the plate between the free end of the lever and the adjacent edge of the plate with the axis of its threaded bore intersecting the axis of rotation of the eccentric, a screw threaded in said nut member, a solid block connected to the inner end of the screw to be moved thereby toward and from the lever as the screw is turned, and the free end of the lever having an outwardly facing socket with solid unyielding walls to receive said block.

Osman May 11, 1948 Osman Dec. 28, 1954 

